Final answer:
The equation that represents the value of the car after x years is y = 42,000 - 1,200x.
Step-by-step explanation:
The correct equation to represent the value of the car after x years is y = 42,000 - 1,200x. In this equation, 'y' represents the value of the car and 'x' represents the number of years Roni owns the car. Since the car depreciates by $1,200 per year, we subtract $1,200 for each year, hence the negative sign before 1,200. The initial value of the car is $42,000, so we start with that value.